Material handling vehicles such as lift trucks are used to pick up and deliver loads between stations. A typical lift truck 10 has a mast 12, which supports a load-lifting carriage 14 that can be raised along the mast 12 (see FIG. 1). The carriage 14 typically has one or more carriage bars 16 to which a fork frame 18 is mounted. The carriage bars 16 are coupled to the mast in a way that allows the lift truck 10 to move the carriage bars 16 up and down, but not laterally relative to the truck. The fork frame 18 carries a pair of forks 20. An operator of the lift truck 10 maneuvers the forks 20 beneath a load prior to lifting it.
Instead of forks 20, a lift truck 10 may have a load clamp assembly 22 coupled to its mast 12 (See FIG. 2). The load clamp assembly 22 typically comprises a frame 40, one or more actuators 36 and two clamp arms 34. The actuators 36 are configured to move the clamp arms 34 toward or away from each other. In use, the operator of the lift truck 10 approaches a load to be carried, such as a stack of cartons or a large appliance, such as a refrigerator. As the lift truck 10 approaches the load, the operator uses controls to open the gap between the clamp arms 34 wider than the load and may adjust the height of the clamp arms 34 so they will engage the load in a suitable location. The operator then maneuvers the lift truck 10 to straddle the load between the clamp arms 34. When the clamp arms 34 are positioned suitably around the load, the operator uses controls to bring the clamp arms 34 together, grasping the load. The operator then uses other controls to raise the load clamp assembly 22, raising the load off the floor, the load held between the clamp arms 34 by friction. The operator then drives the load to a desired location.
Load clamps, also known as carton clamps, are well known, but existing designs make it difficult for the operator of the lift truck 10 to see through the frame 40 of the load clamp assembly 22 when it has been raised to a position on the mast 12 right in front of the operator's line of sight (e.g., see FIG. 2). This is inconvenient and can waste time. If the best place to grasp a load requires putting the load clamp assembly 22 at a height in the operator's line of sight, the operator can have difficulty approaching the load. The operator may have to lower the load clamp assembly 22, approach the load, and then raise the load clamp assembly 22 before clamping on to the load. Alternatively, the operator can lean out and look around one side of the load clamp assembly 22 and then lean out the other way and look around the other side of the load clamp assembly 22 when approaching the load. However, this is only effective if the load is somewhat narrow. Most load clamp assemblies 22 can spread the clamp arms 34 farther apart than the operator can lean out. This technique can also be tiring for the operator. Once the load is grasped and lifted, the operator can drive the lift truck in reverse to the desired destination with a clear view looking over their shoulder or in a rear view mirror. Most lift truck operators are well skilled in driving in reverse.